The present invention relates to vehicle suspensions and components thereof. More particularly, the present invention relates to leaf spring suspensions.
Leaf springs are commonly used as active components in vehicle suspensions. Examples of suspensions using a leaf spring are shown and described in U.S. Pat. No. 5,938,221 (Wilson), the disclosure of which is hereby incorporated herein by reference.
One of the shortcomings associated with the design of leaf spring suspensions is due to the fact that in order to lower the vertical spring rate to a desirable level, the leaf spring sometimes must be increased in length beyond the packaging constraints of the vehicle. In particular, in certain vehicles, there are limitations on the space available to accommodate the longer length spring required to achieve a lower spring rate for a given suspension.
Another shortcoming associated with the design of leaf spring suspensions is that the axle travel is conventionally limited by the maximum allowable leaf spring deflection, which is limited by the peak stress of the leaf spring and in turn is a characteristic based on the material of construction for the leaf spring. In some cases, leaf spring suspensions having a desired spring rate cannot be used because the stress imparted upon the leaf spring is too great and/or the maximum allowable leaf spring deflection would not support the load required within the maximum axle travel limits.
Another shortcoming associated with leaf spring suspensions that use air springs is that if the one or more air springs are not balanced about the vehicle axle centerline, excessive deflection and/or high stress gradients could be exerted on the leaf spring during vertical loading and would also add to spring windup during acceleration and braking. For front air suspensions using a single air spring, the maximum vehicle load would necessitate use of a large diameter air spring, which could be difficult to package in the available space.
Another shortcoming associated with leaf spring suspensions is that conventionally the attachment of the leaf spring to the vehicle axle has been carried out in a way that produces a mechanical metal-to-metal connection between the leaf spring and the axle. This conventional means of connecting the leaf spring to the vehicle axle negates utilization of a section of the leaf spring, namely its spring seat section, as part of the active component, giving the leaf spring a shorter effective length than its true physical length and increasing the overall spring rate of the leaf spring. In addition, this metal-to-metal connection can be a limitation of the fatigue life for the leaf spring.
Another shortcoming associated with leaf spring suspensions is that fabricated axle seats have not been applied to front fabricated steer axles. The vehicle components conventionally used have been more costly in terms of manufacturing and material costs. In addition, the conventional vehicle components have been heavier, which in the case of commercial vehicles, translates into reduced payload capacity.
Accordingly, it is desirable to overcome one or more of the foregoing shortcomings, or alternatively other shortcomings not specified herein but associated with prior leaf spring suspensions.
The benefits of the preferred forms of the novel subject matter set forth herein will become apparent from the following description. It will be understood, however, that an apparatus could still appropriate the invention claimed herein without accomplishing each and every one of those benefits gleaned from the following description. The appended claims, not the benefits of the novel subject matter set forth herein, define the subject matter protected by law. Any and all benefits are derived from the preferred forms of the invention, not necessarily the invention in general.